Generally, a window/door has the roles of allowing the outside light to the inside and allowing the outside air to properly ventilate the inside air. In the condition that the window/door is closed, it has the role of keeping the cooling/heating effect of the inside by blocking heat flow between the inside and the outside. As the expansion of a balcony has been legalized and the quality of the standard of living of a city dweller has been improved, it is more important for a window/door to heighten the effect of the inside interior/outside exterior design as well as to strengthen the performance of air tightness and insulation as previously explained.
Windows/doors have various facades by complexly installing fixed windows/doors and/or movable windows/doors. The movable windows/doors are structured to be opened/closed by different ways of opening/closing them by tilting, turning or sliding. Since windows/doors are able to improve the beauty in the view of the interior/exterior design, these have been widely used to a residential building, an officetel (studio apartment) building, etc.
This window/door comprises a window/door frame including a pair of horizontal bars and a pair of vertical bars forming the borders of the window/door, and a pane of glass to be fitted into the window/door frame. The window/door frames according to the conventional art are structured to have a 90 degree joint or 45 degree joint between the horizontal bar and the vertical bar.
A conventional window/door frame having 90 degree joints between a horizontal bar and a vertical bar is assembled as follows: There are prepared a pair of horizontal bars and a pair of vertical bars being each wider than each horizontal bar in width. Next, holes are cut in upper and lower ends of the inner side of each of the vertical bars so that both ends of each of the horizontal bars are fitted into the holes. The horizontal bars are fitted into the holes cut into the vertical bars so that these bars maintain a square frame. The horizontal bars and vertical bars are fixed by using screws. In this conventional window/door frame, since the both ends of each of the horizontal bars are primarily fitted into the both ends of each of the vertical bars and these connected parts are fastened using the screws, the connection of the horizontal bars and vertical bars is relatively strong.
However, in this conventional window/door frame, since the width of the vertical bar is greater than the width of the horizontal bar to fit the horizontal bar into the hole cut into the vertical bar, a raised step occurs in the joint of the vertical bar and the horizontal bar. That is, since the raised step occurs in the joint of the vertical bar and the horizontal bar, a sense of beauty of the window/door frame greatly decreases. Further, in the case where pattern is formed on the surfaces of the vertical bars and the horizontal bars, the pattern formed on the surfaces of the vertical bars and the pattern formed on the surfaces of the horizontal bars fails to continue and disconnects by the raised step of the joints, lessing the sense of beauty.
A prefabricated window/door structure with 45 degree joints has been developed because of the aforementioned problems of the prefabricated window/door structure with the 90 degree joints. In the prefabricated window/door structure with 45 degree joints, both ends of a vertical bar are cut at an angle of 45 degrees and both ends of a horizontal bar are cut at an angle of 45 degrees. One of the ends of the vertical bar being cut at an angle of 45 degrees faces one of the ends of the horizontal bar being cut at an angle of 45 degrees. In this case, since the thickness of the vertical bar is the same as the thickness of the horizontal bar, no raised step occurs between them. A “┐”-shaped fixing piece is inserted into the corner where the vertical bar is connected with the horizontal bar. Then, the fixing piece is punched to increase the thickness of the fixing piece at the part being punched. The joint of the vertical bar and the horizontal bar is secured by the thickness of the fixing piece.
However, the prefabricated window/door structure with 45 degree joints has the problems:
First, the thickness of the vertical bar and the horizontal bar need to be thick in order to properly secure the joint of the vertical bar and the horizontal bar by pressurizing a specific part of the fixing piece and forcibly increasing the thickness of the pressurized part. If the thickness of the vertical bar and the horizontal bar is thin, the parts of the vertical bar and horizontal bar being secured by the fixing piece separate when the thickness of the fixing piece changes. Therefore, the fixing piece is not tightly fixed inside the vertical bar and horizontal bar. Furthermore, since flowage can occur between the vertical bar and horizontal bar and the fixing piece even by a slight impact, the fixing piece loosens from the joint of the vertical bar and horizontal bar and flowage occurs in the joint. Therefore, the thickness of the vertical bar and horizontal bar needs to be thick to properly fix the vertical bar and horizontal bar by punching the fixing piece. If the thickness of the vertical bar and horizontal bar increases, the binding power with the fixing piece increases but the total weight of the window/door frame increases and therefore it is difficult to be assembled, transported or installed. In addition, the manufacturing unit price is also increased.
Second, when the fixing piece is inserted in the joint of the vertical bar and horizontal bar and it is fixed by punching, it is impossible to separate them again. Therefore, once the window/door fame with 45 degree joints is assembled, it cannot be disassembled. That is, since the prefabricated window/door structure with 45 degree joints is impossible to be disassembled once it is assembled, it is very difficult to maintain or repair it.